This invention relates to a piezoelectric acoustic device, and more particularly to a piezoelectric acoustic device in the form of a piezoelectric speaker, a piezoelectric buzzer or the like which is used for an electronic equipment such as a portable telephone or the like.
In general, a piezoelectric acoustic device includes a casing made of an insulating resin material or the like and a piezoelectric vibrator received in the casing. In recent years, it is highly demanded to small-size an electronic equipment and provide it with multiple functions. For this purpose, it is required that the electronic equipment is provided on a surface thereof or an operation face section thereof with parts for multi-functioning. The parts include, for example, a liquid-crystal display element for a telephone receiver, various kinds of switches and the like. Arrangement of such additional parts on the operation face section of the electronic equipment or large-sizing of the parts requires to increase an area of the operation face section. However, an increase in area of the operation face section is contrary to small-sizing of the electronic equipment.
A piezoelectric acoustic device which has been conventionally used for such an electronic equipment is disclosed in, for example, Japanese Utility Model Publication No. 879/1984, Japanese Patent Application Laid-Open Publication No. 75578/1994, Japanese Patent Application Laid-Open Publication No. 28167/1995, U.S. Pat. No. 3,970,879, U.S. Pat. No. 4,122,365, U.S. Pat. No. 4,183,017 and the like. The piezoelectric acoustic device disclosed is generally constructed in the form of a piezoelectric buzzer or a piezoelectric speaker which includes a casing and a drum provided at a substantially central portion of a front side wall of the casing in a manner to communicate with the casing. Unfortunately, the conventional piezoelectric acoustic device fails to increase an area of an operation face section of an electronic equipment because the drum is arranged at the substantially central portion of the front side wall of the casing.